1. Field of the Invention
The present invention relates to a method of producing, in workpieces, bores having a high surface quality or finish; the method is particularly applicable to producing cylinder bores in engine cylinder blocks. The present invention also relates to an apparatus for carrying out such a method.
2. Description of the Prior Art
With heretofore known methods, a deterioration of the surface quality of the bore frequently occurs in that region where a reversal of direction of the stroke movement of a honing tool occurs. With regard to the preferred application of the present invention, namely for the production of cylinder bores, for example in engine cylinder blocks, reversals of the stroke movement are effected at locations of the honing tool not only in the region of the end that faces the cylinder head, but also in the region of that end of the cylinder block that faces the crankshaft. In these regions of the stroke reversal, it is not possible pursuant to the state of the art to maintain a honing angle value that is favorable with regard to the oil adhesion and sealing achieved with the piston rings. This honing angle refers to the angle of intersecting, linear machining scoring resulting from the stroke and rotational movements of the tool. In the deceleration and acceleration regions, the angle is less than the desired value, while the angle is 0.degree. at the reversal points. Therefore, the appearance the surface of the bore in these regions is not uniform. Rather, in conformity with the number and arrangement of the engaging honing stones, more or less small sections having short curved machining scorings are present; these sections represent an undesired deterioration of the surface quality.
Attempts have been made to eliminate the aforementioned drawbacks by disposing pairs of engine cylinder blocks in opposite directions with their cylinder head ends abutting one another; the aligned cylinder bores of a given pair of engine blocks are then machined as a single bore. However, in so doing, the damaging affect of the surface quality can be avoided for only that region of the cylinder bore that faces the cylinder head.
In addition, this heretofore known solution requires that the honing tool be introduced into the cylinder bore from the side of the crankshaft. However, with many engine blocks, this is not possible due to the crankshaft bearing members. Thus, in most cases, the heretofore known solution cannot be utilized.
An object of the present invention is to provide a method of the aforementioned general type, as well as an apparatus for carrying out such a method, whereby the aforementioned drawback, namely the affect that the reversal of movement of a honing tool has upon the surface quality of a bore, is avoided.